The present invention relates to text fixtures for conducting electrical testing of electrical devices such as integrated circuit dies and leadless integrated circuit carriers, and more particularly to an improved apparatus for providing electrical connections to such devices without the use of fragile wire fingers or wire bond connections.
IC dies are formed when a multiple circuit substrate is scribed and cut into individual dies or chips. Each die has a plurality of terminal pads formed on a surface thereof, to which electrical connections are made to connect the IC die into a circuit.
Leadless integrated circuit (IC or "chip") carriers are in widespread use for mounting IC dies. These chip carriers typically are fabricated from ceramic, and have a substantially planar configuration, with a plurality of closely spaced contact terminals formed around the external periphery of the carrier. A printed wiring pattern is formed on an upper surface of the chip carrier. The IC die is bonded to a surface of the carrier, with electrical terminal being made between contact pads on the IC die and pad locations on the printed wiring pattern, e.g., by wirebonds. The wiring pattern connects the pad locations to predetermined leadless carrier terminals, typically located on the external periphery of the chip carrier.
Leadless chip carriers are conventionally soldered onto a printed circuit board, with the peripheral chip terminals soldered at predetermined locations on the board printed wiring diagram. However, prior to mounting the chip carrier, it is desirable to test the chip carrier and the IC die(s) mounted on the chip carrier to determine that the IC die is functional and that electrical continuity exists between the chip terminal pads and the printed wiring pattern on the surface of the chip carrier.
In the past, test fixtures have been used which employ wire fingers or wiskers arranged in the peripheral configuration of the carrier to be tested. As the leadless chip carrier is inserted into the fixture, the peripheral contact terminals of the carrier are brought into electrical contact with the wire fingers of the fixture. These conventional test fixtures are expensive and the wire fingers are fragile. Moreover, a different fixture configuration is required for each type of device to be tested, since electrical contacts are achieved by the matching of the locations of the wire fingers to the peripheral contact terminal configuration of the chip carrier. Since a typical center-to-center spacing of the carrier contacts is 0.020 inches, with some forty to sixty-odd terminals per side of the carrier, the complexity of the conventional test fixture, with one wire finger or wisker corresponding to each contact terminal on the chip carrier, may be readily appreciated.
It would therefore represent an advance in the art to provide a connector apparatus for testing leadless chip carriers and associated IC dies which does not employ wire fingers or wire bonding to make electrical contact with the carrier, and which is relatively inexpensive and rugged.